The present invention relates to a beam shoe for attaching a (first) beam end-on to a load-bearing construction, especially to a second beam disposed in the same plane as the beam to be attached and running at right angles thereto, the beam shoe comprising an originally flat, one-piece, strip-like sheet-metal portion or blank, which is shaped to an upwardly open channel-shaped retaining member having a web-like rectangular bottom for bracing the beam to be attached on the beam shoe as well as two web-like, parallel retaining legs, the retaining member embracing, in assembled condition, an end portion of the beam to be attached at the underside and side faces thereof, the legs, which are bent over upwardly from the bottom at right angles and disposed along two opposite borders of the bottom, being provided with through holes for rod-like fasteners such as nails in particular in order to join the beam shoe to the beam to be attached, the inside spacing of the legs therefore being (at least) as large as (and if necessary somewhat larger than) the width of the beam to be attached, wherein a fastening flange provided with through holes for rod-like fasteners such as nails and/or screws is bent over at right angles along that longitudinal border of each retaining leg which faces the load-bearing construction (or if necessary the second beam), the fastening flange being designed to be placed with its outside face remote from the channel-shaped retaining member of the beam shoe on the load-bearing construction/the second beam and to be fastened thereto with rod-like fasteners such as nails and/or screws, and wherein the web-like bottom is reinforced by a (bottom) reinforcing flange or the like in order to increase its section modulus against sagging under relatively large load.
Beam shoes are used in wood construction for attachments of solid or glued laminated beams in the same plane. They have the advantage among others of simple, rapid and reliable assembly, without weakening the wood members at the attachment point.
Besides beam shoes having fastening flanges bent over outwardly at right angles from the retaining legs, there are known beam shoes having fastening flanges bent over inwardly at right angles from the retaining legs. Furthermore, there is also known a beam shoe which, instead of being provided with the two fastening shoes bent over from the retaining legs, is provided with a back wall running between the retaining legs, a fastening flange provided with through holes for rod-like fasteners for mounting the beam shoe on a second beam being bent over at right angles at the upper end of the back wall.
Beam shoes having two fastening flanges are generally fastened first to a main beam of the load-bearing construction. Thereafter the beam to be attached is inserted in the beam shoe assigned to it in such a way that it is braced on the bottom thereof and can then be nailed to the retaining legs.
Common to all known beam shoes is that—simply for cost reasons—they are made from an originally flat, one-piece sheet-metal portion (blank) which, after being cut out or stamped from heavy sheet metal of predetermined thickness, is shaped by means of appropriate machines or tools. In this operation, it is therefore very important from economic viewpoints to organize the shaping of the beam shoe in such a way that cutting of the blank can be achieved with the lowest possible losses and preferably without losses.
In beam shoes of the class in question, without bottom reinforcing flange, undesired or possibly even inadmissible sagging of the beam-shoe bottom occurs during relatively large load on the beam to be attached as a result of transverse forces acting vertically on the bottom of the beam shoe. In order to counteract or at least largely prevent this “cable effect”, bead-like stiffening ribs have been pressed into the bottom, but they have not led to an adequate increase of the section modulus compared with an unshaped bottom.
For this reason a reinforcing flange bent over at right angles inwardly or upwardly or else outwardly or downwardly has already been provided along the border of the beam-shoe bottom. In the finished beam shoe, this reinforcing flange is disposed in the plane of the two fastening flanges and protrudes perpendicularly from the bottom in the manner of a tongue. Nevertheless, even these configurations are not yet satisfactory for the desired goal of a substantially bending-proof bottom, since these tongues are narrower than the bottom and therefore are joined only to that bottom, but not to the retaining legs, and so the section modulus can be increased to only a limited extent in the lower portion of the channel-shaped retaining member.
A further disadvantage of known beam shoes of the class in question is that their blanks cannot be cut with low losses or even without losses, since the sheet-metal portion forming the reinforcing flange in the finished beam shoe protrudes in the manner of a tongue beyond the same bending line of the blank in the region of the middle blank portion forming the bottom after shaping. From this portion there is extended, into the two outer end portions of the strip-like sheet-metal blank, that portion which, after shaping, corresponds to the contour of the sheet-metal portion protruding in the manner of a tongue and forming the fastening flanges but not to the contour of the strip-like blank along the longitudinal border thereof. Under the best circumstances, therefore, it has been possible to counter this loss (of sheet metal) only if the portion of the blank forming the bottom is appropriately recessed along its border opposite the reinforcing-flange portion. However, this feature would lead to weakening of the bottom, even though its bending resistance is supposed to be increased with this feature.
Furthermore, it must be considered that the sheet-metal thickness of any wood fasteners will be kept as small as possible for cost reasons, although at the same time it has been assumed heretofore that the sheet-metal thickness of beam shoes for common applications must not be less than 2 mm precisely because of the feared bottom sagging.